On the other hand: poverty is invariably measured by national standards, so it is difficult to compare poverty rates across countries. Usually, a person or family is said to be “poor” if their annual income is, say, less than 60% of the median annual income of the country. Because the United States’ middle class is wealthy and the country enjoys the world’s highest median household income, the standard by which someone is said to be poor is also the highest. Thus, even though America’s poverty rate is more than twice that of Sweden, 40% of Swedish households earned less than $25,000 (international dollars) in 2010, compared to 26% of American households in the same income bracket that year. Overall, the United States still enjoys a very high standard of living by most measures. The ., for example, ranks the . as having the third-highest Human Development Index; tied with the Netherlands; below Norway and Australia; and slightly above New Zealand, Canada, and Ireland.
Because the majority of people today (and in Quetelet's time) lead fairly sedentary lives and are not particularly active, the formula tacitly assumes low muscle mass and high relative fat content. It applies moderately well when applied to such people because it was formulated by focusing on them. But it gives exactly the wrong answer for a large and significant section of the population, namely the lean, fit and healthy. Quetelet is also the person who came up with the idea of "the average man." That's a useful concept, but if you try to apply it to any one person, you come up with the absurdity of a person with children. Averages measure entire populations and often don't apply to individuals.